Ultra-hard material cutting elements, methods of forming the same and bits incorporating the same

ABSTRACT

The present disclosure relates to cutting tools incorporating polycrystalline diamond bodies used for subterranean drilling applications, and more particularly, to a polycrystalline diamond body joined to a substrate by a fastening member to form a cutting element. The polycrystalline diamond body may be binderless polycrystalline diamond, non-metal catalyst polycrystalline diamond, leached polycrystalline diamond, carbonate polycrystalline diamond or polycrystalline cubic boron nitride. The polycrystalline diamond body includes an aperture and a fastening member extending through the aperture and metallurgically bonded to the substrate by a HPHT process.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/717,070 filed on Oct. 22, 2012, which is incorporated herein by reference in its entirety.

BACKGROUND

Ultra-hard materials are often used in cutting tools and rock drilling tools. Polycrystalline diamond material is one such ultra-hard material, and is known for its good wear resistance and hardness, making it a popular material choice for use in such industrial applications as cutting tools for machining and wear and cutting elements in subterranean mining and drilling.

To form polycrystalline diamond, diamond particles are sintered at high pressure and high temperature (HPHT sintering) to produce an ultra-hard polycrystalline structure. A catalyst material may be added to the diamond particle mixture prior to sintering and/or infiltrates the diamond particle mixture during sintering in order to promote the intergrowth of the diamond crystals during HPHT sintering, to form the polycrystalline diamond (PCD) structure. Metals conventionally employed as the catalyst are selected from the group of solvent metal catalysts selected from Group VIII of the Periodic table, including cobalt, iron, and nickel, and combinations and alloys thereof. After HPHT sintering, the resulting PCD structure includes a network of interconnected diamond crystals bonded to each other, with the catalyst material occupying the interstitial spaces or pores between the bonded diamond crystals. The diamond particle mixture may be HPHT sintered in the presence of a substrate, to form a PCD body bonded to the substrate. The substrate may also act as a source of the metal catalyst that infiltrates into the diamond particle mixture during sintering.

A desired property of PCD bodies used for certain applications is improved thermal stability during wear or cutting operations. A problem known to exist with conventional PCD bodies is that they are vulnerable to thermal degradation when exposed to elevated temperatures. This vulnerability results from the differential that exists between the thermal expansion characteristics of the solvent metal catalyst material disposed interstitially within the PCD body and the thermal expansion characteristics of the intercrystalline bonded diamond. The material damage caused by such differential thermal expansion is known to start at temperatures as low as 400° C., and can induce thermal stresses that can be detrimental to the intercrystalline bonding of diamond and eventually result in the formation of cracks that can make the PCD structure vulnerable to failure. Further, the solvent metal catalyst is known to cause an undesired catalyzed phase transformation in diamond (converting it to graphite) with increasing temperature, thereby limiting practical use of the PCD body to about 750° C.

Thermally stable PCD materials have been developed to improve performance at high temperatures. However, it can be difficult to form a bond between the thermally stable PCD material and a substrate, for attachment to a cutting tool. Due to the high brittleness and high hardness of thermally stable PCD materials, machining conventional features, such as threads, on the PCD body or the carbide is not feasible. Accordingly, it is difficult to join the thermally stable PCD material and a substrate by conventional mechanical methods.

SUMMARY

The present disclosure relates to cutting tools incorporating polycrystalline diamond bodies used for subterranean drilling applications, and more particularly, to a thermally stable polycrystalline diamond (PCD) body joined to a substrate by one or more fastening elements to form a cutting element. In an embodiment, a cutting element includes a thermally stable polycrystalline diamond body mechanically joined to a carbide substrate with a fastening element. The thermally stable PCD body may be binderless PCD, non-metal catalyst PCD such as a carbonate PCD, or leached PCD. In an embodiment, a method is provided for joining a thermally stable polycrystalline diamond body to a substrate. The method includes forming a thermally stable PCD body, which may be binderless PCD, non-metal catalyst PCD, or leached PCD. The method includes forming an aperture in the thermally stable PCD body for receiving the fastening element, and inserting the fastening element into the aperture. The method also includes positioning the thermally stable PCD body and fastening element on the substrate. The method also includes subjecting the thermally stable PCD, the fastening element, and the substrate to high pressure high temperature (HPHT) sintering to bond the fastening member to the substrate.

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of thermally stable PCD materials mechanically fastened to substrates are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components.

FIG. 1 illustrates a region of a thermally stable non-metal catalyst PCD material, in accordance with an embodiment.

FIG. 2 illustrates a region of a thermally stable binderless PCD material, in accordance with an embodiment.

FIG. 3 illustrates a region of a thermally stable leached PCD material, in accordance with an embodiment.

FIG. 4 illustrates an exploded view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 5 illustrates a perspective view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 6 illustrates a cross-sectional view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 7 illustrates an exploded view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 8 illustrates a perspective view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 9 illustrates a cross-sectional view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 10 illustrates an exploded view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 11 illustrates a perspective view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 12 illustrates a cross-sectional view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 13 illustrates an exploded view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 14 illustrates a perspective view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 15 illustrates a cross-sectional view of a cutting element having a thermally stable PCD body, a substrate and a fastening member in accordance with an embodiment.

FIG. 16 illustrates example method(s) for fastening a thermally stable PCD body to a substrate, in accordance with one or more embodiments.

FIG. 17 illustrates example method(s) for fastening a thermally stable PCD body to a substrate, in accordance with one or more embodiments.

FIG. 18 illustrates an example device incorporating a cutting element, in accordance with an embodiment.

DETAILED DESCRIPTION

The present disclosure relates to cutting tools, such as shear cutters on a drill bit, incorporating polycrystalline diamond bodies used for subterranean drilling applications, and more particularly, to a thermally stable polycrystalline diamond (PCD) body joined to a substrate by one or more fastening elements to form a cutting element. In an embodiment, the thermally stable PCD material may be binderless PCD, non-metal catalyst PCD, or leached PCD. The thermally stable PCD body includes an aperture to receive the fastening element securing the thermally stable PCD body to the substrate. The fastening element is subsequently metallurgically bonded to the substrate to mechanically fasten the PCD body to the substrate. The fastening element may also be metallurgically bonded to the PCD body.

The following disclosure is directed to various embodiments. The embodiments disclosed have broad application, and the discussion of any embodiment is meant only to be descriptive of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment or to the features of that embodiment.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art would appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name only. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness.

As used herein, a plurality of items, structural elements, compositional elements and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.

Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

For clarity, as used herein, the term “conventional PCD” refers to conventional polycrystalline diamond that has been formed with the use of a conventional metal catalyst during an HPHT sintering process, forming a microstructure of bonded diamond crystals with the metal catalyst material occupying the interstitial spaces or pores between the bonded diamond crystals.

“Non-metal catalyst PCD” refers to PCD material that has been formed with the use of a non-metal catalyst during an HPHT sintering process, forming a microstructure of bonded diamond crystals with the non-metal catalyst material occupying the interstitial spaces or pores between the bonded diamond crystals. Examples of non-metal catalysts include carbonates (e.g., MgCO₃), sulfates (e.g., MgSO₄), hydroxides (e.g., Mg(OH)₂), and iron oxides (e.g., FeTiO₃). A carbonate catalyst may be any Group I or Group II carbonate, such as magnesium carbonate, calcium carbonate, lithium carbonate, or sodium carbonate, or combinations of carbonates. “Binderless PCD” refers to a polycrystalline diamond matrix that is formed without the use of a catalyst, such as by converting graphite directly to diamond at ultra-high pressure and temperatures. “Leached PCD” refers to a PCD material that has been treated following the HPHT sintering process to remove at least a portion of the catalyst material formed in the interstitial regions between the bonded diamond crystals and, thus, comprises a plurality of interstitial regions that are substantially free of the catalyst material (i.e., the interstitial regions between the bonded diamond crystals are substantially empty voids or pores). “Thermally stable PCD” as used herein means non-metal catalyst PCD, binderless PCD or leached PCD. In an embodiment, the thermally stable PCD is selected from the group consisting essentially of non-metal catalyst PCD, binderless PCD, and leached PCD. Examples of suitable devices for performing the HPHT sintering process include a cubic press, a belt press, and a toroid press.

A region of non-metal catalyst PCD material 10 is schematically illustrated in FIG. 1. This microstructure of non-metal catalyst PCD 10 is formed by subjecting a diamond powder mixed with a non-metal catalyst, such as carbonate, to an HPHT sintering process. In one embodiment, the HPHT sintering process includes applying a pressure of about 70 kbar or greater, and a temperature of about 2,000 to 2,500° C. At this temperature and pressure, the non-metal catalyst material melts and infiltrates through the diamond powder mixture. The catalyst promotes the growth of diamond crystals during the HPHT sintering process, forming non-metal PCD. The resultant non-metal catalyst PCD material 10 has a polycrystalline microstructure including multiple diamond grains or crystals 11 bonded to each other, with non-metal catalyst material 12, such as carbonate, occupying interstitial spaces or pores between the diamond crystals 11. When a non-metal catalyst is used, the diamond remains thermally stable in polycrystalline diamond form with increasing temperature up to 1200° C., rather than being converted to graphite. Additionally, non-metal catalysts may decompose under heat and produce gases. Accordingly, the material damage due to the thermal expansion mismatch between the PCD and the non-metal catalyst is negligible with increasing temperature. In an embodiment, the size of the diamond crystals 11 in the non-metal PCD material 10 is about 1-50 microns. In another embodiment, the size in the diamond crystals 11 is less than 1 micron. In one embodiment, the non-metal catalyst PCD 10 is made up of about 90-98% diamond by volume. In another embodiment, the non-metal catalyst PCD 10 has a diamond volume content of at least 99%. In another embodiment, the non-metal catalyst PCD 10 has a diamond volume content of at least 95%. In another embodiment, the non-metal catalyst PCD 10 has a diamond volume content of at least 90%.

A region of binderless PCD material 20 is schematically illustrated in FIG. 2. This microstructure of binderless PCD 20 is formed by subjecting carbon (such as graphite, buckeyballs, or other carbon structures) without a catalyst material to an ultra-high temperature and pressure sintering process. In one embodiment, this process includes HPHT sintering at ultra-high temperature and pressure, above that applied during conventional HPHT sintering to form PCD. In one embodiment, the pressure is between about 100-160 kbar, such as about 150 kbar, and the temperature is about 2200-2300° C. For example, when sintering graphite, the pressure may be about 150 kbar, or about 150-160 kbar. When sintering other types of carbon, such as buckeyballs or other complex carbon structures, the pressure may be about 110-120 kbar. For reference, conventional HPHT sintering to form PCD may be performed at about 55-60 kbar. The resultant binderless PCD 20 has a polycrystalline microstructure including multiple diamond grains or crystals 21 bonded to each other, without catalyst material interspersed between the diamond crystals 21 (i.e., the diamond crystals 21 of a binderless PCD 20 are bonded directly to each other, and are substantially devoid of gaps or interstitial spaces between the diamond crystals 21). The binderless PCD 20 is substantially pure carbon, with a diamond volume fraction greater than 99%.

In one embodiment the material microstructure of the binderless PCD material 20 has a diamond volume content of at least 98%, and in another embodiment at least or about 99%, and in another embodiment at least or about 99.5%, and in another embodiment at least or about 99.8%, and in another embodiment at least or about 99.9%. In one embodiment, the binderless PCD material 20 has a fine diamond grain size, such as an average diamond grain size less than 1 micron, such as about 50 nm or less. In other embodiments, the binderless PCD material 20 has an average grain size of about 1-30 microns.

In another embodiment, the thermally stable binderless diamond material is formed by depositing layers in a chemical vapor deposition (CVD) process, to form a binderless PCD material 20 with substantially 100% diamond volume content. The CVD process is performed by heating gas precursors in a reactive environment, which results in the precursors reacting or decomposing on the surface of a substrate, forming the desired deposit. This process results in growth of diamond crystals on the substrate.

Binderless PCD is thermally stable because it does not suffer from differential thermal expansion between diamond and catalyst. The binderless PCD has one phase, and thus there is no differential thermal expansion between different phases of the material. As a result, diamond bodies formed from this binderless PCD material can exhibit high strength even at elevated temperatures, whereas conventional PCD suffers from thermal degradation due to the differential expansion of the diamond and catalyst phases.

A region of leached PCD material 30 is schematically illustrated in FIG. 3. This microstructure of leached PCD 30 is formed by subjecting a diamond powder mixed with a catalyst to an HPHT sintering process. The resultant PCD material has a polycrystalline microstructure including multiple diamond grains or crystals bonded to each other, with catalyst material occupying interstitial spaces or pores between the diamond crystals. The PCD material is subsequently treated to remove the catalyst material from the plurality of interstitial regions. Accordingly, leached PCD 30 comprises a plurality of bonded together diamond crystals 31 and a plurality of interstitial regions 32 between the bonded diamond crystals 31 substantially free of the catalyst material. Leaching may be performed by placing the PCD body in an acid solution in a Teflon container, which is contained within a sealed stainless steel pressure vessel and heated to 160-180° Celsius. Pressures between 100-200 psi are likely achieved by heating the acid solution under these conditions. Suitable acid solutions for leaching include reagent grade acids comprising a concentration of approximately 5.3 mol/liter HNO3 and approximately 9.6 mol/liter HF, which is made by ratio of 1:1:1 by volume of HNO3-15.9 mol/liter (reagent grade nitric acid): HF-28.9 mol/liter (regent grade hydrofluoric acid): and water.

During a mining or drilling operation, shear cutters on the drill bit may experience high loads (e.g., between 2500 and 3000 lbs on a cutting edge of the shear cutters). Accordingly, forming a strong bond between the thermally stable PCD body and the substrate may enable the shear cutters to withstand these high loads. Bonding a thermally stable PCD body to a substrate can present a challenge because a thermally stable PCD body is formed without a conventional catalyst metal, such as cobalt. In a conventional PCD, the metal solvent catalyst used to facilitate diamond growth during HPHT sintering also forms a bond between the conventional PCD body and the substrate. In contrast, a thermally stable PCD body lacks a metal solvent catalyst to form a bond between the thermally stable PCD body and the substrate. Non-metal catalyst PCD includes non-metal catalyst occupying the interstitial spaces (see FIG. 1), binderless PCD lacks interstitial spaces between the bonded diamond crystals (see FIG. 2), and leached PCD is substantially free of catalyst in the interstitial spaces or voids between the bonded diamond crystals (see FIG. 3). Accordingly, non-metal catalyst PCD and binderless PCD lack empty interstitial spaces between the bonded diamond crystals available to be filled with a bonding material (such as a metal solvent catalyst) that flows between the substrate and the PCD, as during conventional HPHT sintering. Moreover, in an embodiment in which a portion of the PCD body is leached, the leached PCD body may have catalyst material between the bonded diamond crystals along the interface surface between the leached PCD body and substrate. Accordingly, leached PCD may lack empty interstitial spaces to be infiltrated with a bonding material that flows between the substrate and the leached PCD body. Moreover, brazing a PCD body to a substrate may cause graphitization of the diamond surface during brazing due to the high braze temperatures, destroying the PCD structure and the bond between the PCD body and the substrate.

According to an embodiment illustrated in FIGS. 4-6, a thermally stable PCD body 41 (such as non-metal catalyst PCD, binderless PCD, or leached PCD) is joined to a substrate 42 via a fastening member 43 to form a cutting element 40. The fastening member 43 is used to mechanically lock a thermally stable PCD body 41 to the substrate 42. The thermally stable PCD body 41 includes a top or working surface 44, an interface surface 45 opposite the working surface, and sidewall 46 extending between the working surface 44 and the interface 45. The thermally stable PCD body 41 also includes a cutting edge 47 where the sidewall 46 meets the working surface 44. The cutting edge 47 is the portion of the thermally stable PCD body 41 that engages the formation, such as during a subterranean mining or drilling operation. The interface surface 45 is the portion of the thermally stable PCD body 41 that abuts the substrate 42 when the thermally stable PCD body 41 joins the substrate 42 to form the cutting element 40. In another embodiment, the thermally stable PCD 41 may be joined to an intermediate layer, and the intermediate layer may be joined to the substrate 42.

In an embodiment, the cutting element 40 is formed in two separate HPHT sintering processes. In one embodiment, the cutting element 40 is formed by pre-forming the thermally stable PCD body 41 in a first HPHT sintering process and subsequently joining the thermally stable PCD body 41 to the substrate 42 via a fastening member 43 in a second HPHT sintering process (i.e., the thermally stable PCD body 41 is first formed by HPHT sintering before a second HPHT bonding process is performed to secure the thermally stable PCD body 41 to the substrate 42). The thermally stable PCD body 41 formed in the first HPHT sintering process may be either non-metal catalyst PCD (such as carbonates, sulfates, hydroxides and iron oxides), binderless PCD, or leached PCD. In an embodiment, the first HPHT sintering process is performed on a pre-sintered or pre-compacted PCD body to form the thermally stable PCD body 41. An aperture 48 is subsequently formed in the thermally stable PCD body 41 to receive the fastening member 43 joining the thermally stable PCD body 41 to the substrate 42. In the embodiment illustrated in FIGS. 4 and 6, the aperture 48 is comprised of an axial through hole extending between the working surface 44 and the interface surface 45 of the thermally stable PCD body 41. The through hole extends along a longitudinal axis 49 of the cutting element 40. In an embodiment, the aperture 48 in the thermally stable PCD body 41 may be formed by laser cutting, electrical discharge machining (EDM), or any other suitable process known in the art. In another embodiment, the aperture 48 in the thermally stable PCD body 41 may be formed in the net-shape during the first HPHT sintering process.

With continued reference to an embodiment illustrated in FIG. 4, the substrate 42 comprises an interface surface 50 that abuts the interface surface 45 of the thermally stable PCD body 41 when the substrate 42 is joined to the thermally stable PCD body 41 to form the cutting element 40. In an embodiment, the interface surface 50 of the substrate 42 includes an aperture 51 for receiving a portion of the fastening member 43. The aperture 51 in the substrate 42 may be formed by machining techniques known in the art or any other suitable process. The aperture 51 is formed on the interface surface 50 of the substrate 42 and extends therethrough into the substrate 42. The aperture 51 in the interface surface 50 of the substrate 42 is a generally cylindrical recess extending down along the longitudinal axis 49 of the cutting element 40. In one embodiment, the cylindrical recess 51 in the substrate 42 is concentric with the through hole 48 in the thermally stable PCD body 41 (i.e., the aperture 51 in the substrate 42 is configured for axial alignment with the aperture 48 in the thermally stable PCD body 41). In one embodiment, the aperture 51 in the substrate 42 includes a lower surface 52 and a sidewall 53 extending between the lower surface 52 and the interface surface 50 of the substrate 42. In an embodiment, the lower surface 52 of the aperture 51 in the substrate 42 is generally parallel to the interface surface 50 of the substrate 42. In an embodiment, the diameter of the aperture 48 in the thermally stable PCD body 41 is substantially equal to the diameter of the aperture 51 in the substrate 42.

In an embodiment illustrated in FIGS. 4-6, the fastening member is a pin 43 having a head portion 54 and a relatively smaller shaft portion 55 protruding downward from the head portion 54. In the illustrated embodiment, the shaft portion 55 is generally concentric with the head portion 54 of the fastening member 43. In an embodiment, the head portion 54 of the fastening member 43 is generally disc-shaped and the shaft portion 55 is generally cylindrical. In other embodiments, the head portion of the pin 43 may be domed, square or any other suitable shape. Moreover, the shaft portion 55 of the pin 43 may have a non-circular cross-section, such as a generally square cross-section. In the illustrated embodiment, the head portion 54 of the pin 43 has opposing top and bottom flat surfaces 56, 57, respectively. The shaft portion 55 protrudes downward from the lower surface 57 of the head portion 54 and has a flat, lower surface 58 opposite the bottom surface 57 of the head portion 54. In an embodiment, the outer diameter of the shaft portion 55 of the pin 43 is generally equal to the diameter of the apertures 48, 51 in the thermally stable PCD body 41 and the substrate 42, respectively. In another embodiment, the outer diameter of the shaft portion 55 of the pin 43 is slightly smaller than the diameter of the apertures 48, 51 in the thermally stable PCD body 41 and the substrate 42, respectively. The fastening member 43 can be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof. Examples include carbides such as WC, W 2 C, TiC, VC. In an embodiment, the fastening member 43 is formed of cemented tungsten carbide (e.g., WC-Co). The fastening member 43 may be formed of a matrix material having a tungsten carbide aggregate and a cobalt binder matrix. The fastening member 43 may be formed by sintering or other techniques known in the art. Similarly, the substrate 42 can be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof, such as WC, W 2 C, TiC, VC. In one embodiment, the substrate 42 is formed of cemented tungsten carbide. In an embodiment, the fastening member 43 and the substrate 42 are formed from substantially similar materials, although the fastening member 43 and the substrate 42 may be formed from dissimilar materials. In one embodiment, the fastening member 43 and the substrate 42 may be formed from cemented tungsten carbide. In one embodiment, the fastening member 43 comprises 313 grade carbide (3 μm average WC grain size and 13% Co) and the substrate 42 comprises 406 grade carbide (4 μm average WC grain size and 6% Co). In another embodiment, the fastening member 43 comprises 313 grade carbide and the substrate 42 comprises 812 grade carbide (8 μm average WC grain size and 12% Co). In a further embodiment, the fastening member 43 comprises 406 grade carbide and the substrate 42 comprises 313 grade carbide. In another embodiment, the fastening member 43 comprises 812 grade carbide and the substrate 42 comprises 313 grade carbide. In another embodiment, the fastening member 43 and the substrate 42 are formed from carbides having different binder phases. However, the present disclosure is not limited to the carbide grades recited above, and the fastening member 43 and the substrate 42 may comprise any other suitable combinations of carbides.

After the apertures 48, 51 have been formed in the thermally stable PCD body 41 and the substrate 42, respectively, the thermally stable PCD body 41 is positioned on top of the substrate 42 in a stacked configuration such that the aperture 48 in the thermally stable PCD body 41 is axially aligned with the aperture 51 in the substrate 42, as illustrated in FIGS. 5 and 6. Subsequently, the fastening member 43 may be inserted through the aperture 48 in the thermally stable PCD body 41 and into the aperture 51 in the substrate 42 (i.e., the fastening member 43 extends longitudinally through the apertures 48, 51 in the thermally stable PCD body 41 and the substrate 42, respectively). In an embodiment, the fastening member 43 may be received in the apertures 48, 51 with a press fit (friction fit) or a loose fit. In an embodiment, the length L of the shaft portion 55 of the fastening member 43 is substantially equal to the combined depth D of the aperture 51 in the substrate 42 and the thickness T of the thermally stable PCD body 41. Accordingly, when the fastener 43 is inserted into the apertures 48, 51, the bottom surface 57 of the head portion 54 of the fastening member 43 abuts the working surface 44 of the thermally stable PCD body 41, and the lower surface 58 of the shaft portion 55 of the fastening member 43 abuts the lower surface 52 of the aperture 51 in the substrate 42, as shown in FIG. 6. In another embodiment, when the fastener 43 is inserted into the apertures 48, 51, the bottom surface 57 of the head portion 54 of the fastening member 43 is spaced apart from the working surface 44 of the thermally stable PCD body 41, and the lower surface 58 of the shaft portion 55 of the fastening member 43 is spaced apart from the lower surface 52 of the aperture 51 in the substrate 42. Subsequently, the thermally stable PCD 41, the fastening member 43, and the substrate 42 are placed into a press (e.g., a cubic press, a belt press, a toroid press, etc.) and a second HPHT process is then performed to mechanically secure the thermally stable PCD body 41 to the substrate 42 with the fastening member 43. After the second HPHT process, the bottom surface 57 of fastening member 43 and the lower surface 58 of the fastening member 43 abut surfaces 44, 52, respectively. In an embodiment, the second HPHT process may be performed at pressures ranging between approximately 5.5 GPa and 7 GPa and temperatures ranging between approximately 1300° C. and 1550° C. In another embodiment, the second HPHT process may be performed at approximately 5 GPa.

During the second HPHT process, the fastening member 43 becomes ductile and tends to flow from higher pressure regions to lower pressure regions. In one embodiment, the shaft 55 of the pin 43 can radially expand under the pressure and flow into the apertures 48, 51 in the thermally stable PCD body 41 and the substrate 42, respectively. In this manner, the second HPHT process results in a metallurgical bond between the fastening member 43 and the substrate 42 at the interface between the shaft 55 and the aperture 51 in the substrate 42. Specifically, a metallurgical bond is formed between the outer surface of the shaft 55 and the sidewall 53 of the aperture 51 in the substrate 42, and between the lower surface 58 of the shaft 55 and the lower surface 52 of the aperture 51 in the substrate 42. Depending on the conditions of the second HPHT process, a metallurgical bond may also form at the interface between the thermally stable PCD body 41 and the fastening member 43. In an embodiment, the carbide fastening member 43 becomes ductile during the second HPHT process and a portion of the fastening member 43 infiltrates into the interstitial regions between the bonded diamond crystals of the thermally stable PCD body 41. In one or more embodiments, the cobalt binder matrix of the fastening member 43 enters a liquid state during the second HPHT process and impregnates or infiltrates the interstitial regions disposed between the bonded diamond crystals of the PCD body 41, thereby forming a metallurgical bond between the fastening member 43 and the PCD body 41. Additionally, in one embodiment, a bond may form between the thermally stable PCD body 41 and the carbide substrate 42 along the respective interface surfaces 45, 50. Accordingly, the bond formed between the fastening member 43 and the substrate 42 mechanically secures the thermally stable PCD body 41 to the substrate 42. Moreover, the abutment of the head portion 54 of the fastening member 43 against the working surface 44 of the thermally stable PCD body 41 provides a compressive force securing the thermally stable PCD body 41 to the substrate 42.

The metallurgical bonds described above also avoid sharp contact points and areas of high stress concentration between the fastening member 43, the PCD body 41 and the substrate 42, which could otherwise result from joining an ultra-hard body to a substrate. Because the carbide fastening member 43 and substrate 42 may become ductile during the HPHT process, the carbide may flow and fill in any gaps between the PCD body 41 and the fastening member 43, the PCD body 41 and the substrate 42, and the fastening member 43 and the substrate 42. Accordingly, the flow of the carbide into the various gaps during the HPHT process tends to create smooth interfaces between the PCD body 41, the fastening member 43, and the substrate 42, thereby preventing sharp point or line contacts between the respective parts of the cutting element 40.

Although the PCD body 41 and the substrate 42 are illustrated with planar interface surfaces 45, 50, respectively, the interface surfaces may be non-planar. In one or more embodiments, the interface surface 50 of the substrate 42 may include one or more protrusions (e.g., a domed surface), and the interface surface 45 of the PCD body 41 may include one or more corresponding depressions (e.g., a concave groove) for receiving the protrusions. The protrusions and depressions are configured to join the PCD body 41 to the substrate 42.

In an embodiment illustrated in FIGS. 7-9, a cutting element 70 is formed by mechanically joining a thermally stable PCD body 71 to a substrate 72 with a fastening member 73. In an embodiment, the cutting element 70 is formed by pre-forming the thermally stable PCD body 71 in a first HPHT sintering process and subsequently mechanically joining the thermally stable PCD body 71 to the substrate 72 via the fastening member 73 in a second HPHT sintering process. The thermally stable PCD body 71 formed in the first HPHT sintering process may be either non-metal catalyst PCD (including carbonates, sulfates, hydroxides and iron oxides), binderless PCD, or leached PCD. In an embodiment, the first HPHT sintering process is performed on a pre-sintered or pre-compacted PCD body to form the thermally stable PCD body 71. The thermally stable PCD body 71 includes a working surface 74, an interface surface 75 opposite the working surface 74 and sidewall 76 extending between the working surface 74 and the interface surface 75. The thermally stable PCD body 71 also includes a cutting edge 77 where the sidewall 76 meets the working surface 74.

An aperture 78 is subsequently formed in the thermally stable PCD body 71 to receive the fastening member 73 securing the thermally stable PCD body 71 to the substrate 72. In an embodiment illustrated in FIGS. 7-9, the aperture in the thermally stable PCD body 71 is a notch 78 extending between the working surface 74 and the interface surface 75 of the thermally stable PCD body 71. The notch 78 is comprised of two opposing wall segments 79, 80 which taper inward from the sidewall 76. The two opposing wall segments 79, 80 taper between a wider opening along the sidewall 76 and a narrower opening near the center of the thermally stable PCD body 71. In the illustrated embodiment, the narrower end of the opening includes an interior wall segment 81 extending between the two wall segments 79, 80. Together, the wall segments 79, 80, 81 form a truncated V-shaped opening in the thermally stable PCD body 71.

In the embodiment illustrated in FIG. 7, the notch 78 includes a trapezoidal flange 82 configured to interlock with a portion of the clamp 73. The trapezoidal flange 82 is bounded on three sides by the two tapered wall segments 79, 80 and the interior wall segment 81. The fourth side of the trapezoidal flange 82 is delineated by a vertical wall segment 83 extending between the two tapered wall segments 79, 80. The vertical wall segment 83 is located between the interior wall segment 81 and the opening in the sidewall 76 of the thermally stable PCD body 71. The flange 82 extends upward from the interface surface 75 and toward the working surface 74 of the thermally stable PCD body 71. An upper surface 84 of the flange 82 is recessed from the working surface 74 of the thermally stable PCD body 71. In an embodiment, the thickness T′ of the thermally stable PCD body 71 is approximately twice as thick as the thickness D′ of the flange 82. It is contemplated, however, that the thickness D′ of the flange 82 may include any proportion of the thickness T′ of the thermally stable PCD body 71. In an embodiment, the thickness D′ of the flange 82 corresponds to the portion of the thermally stable PCD body 71 which was not leached to remove the catalyst material from the interstitial regions between the bonded diamond crystals. That is, in an embodiment, the recess formed between the working surface 74 and the upper surface 84 of the flange 82 corresponds to the depth at which the thermally stable PCD body 71 was leached. The notch 78 in the thermally stable PCD body 71 may be formed by laser cutting, electrical discharge machining (EDM), or any other suitable process known in the art. In another embodiment, the notch 78 in the thermally stable PCD body 71 may be formed during the first HPHT sintering process.

With continued reference to the embodiments illustrated in FIGS. 7-9, the fastening member is comprised of a wedge-shaped clamp 73 configured to mechanically secure the thermally stable PCD body 71 to the substrate 72. The clamp 73 generally complements the notched opening 78 in the thermally stable PCD body 71 such that the clamp 73 is configured seat in the notch 78. Moreover, a portion of the clamp 73 is configured to overlap a portion of the notch 78 in the thermally stable PCD body 71 thereby forming a lap joint securing the thermally stable PCD body 71 to the substrate 72.

In an embodiment illustrated in FIGS. 7-9, the clamp 73 is comprised of two tapered wall segments 85, 86, an arcuate sidewall 87 and an end wall 88 opposite the sidewall 87. The clamp 73 also includes an upper surface 89 and an interface surface 90 opposite the upper surface 89. The clamp 73 tapers between the wider sidewall 87 and the relatively narrower end wall 88. Moreover, the clamp is comprised of a relatively thicker portion 91 near the sidewall 87 and a relatively thinner portion 92 near the end wall 88. A step 93 is formed between the thicker and thinner portions 91, 92. In an embodiment, the thicker portion 91 of the clamp 73 is generally equal to the thickness T′ of the thermally stable PCD body 71. In an embodiment, the combined thickness of the thinner portion 92 and the flange 82 is generally equal to the thickness T′ of the thermally stable PCD body 71. The thinner portion 92 of the clamp 73 forms a lip configured to engage the flange 82. The wedge-shaped clamp 73 extends an angle α around the periphery of the cutting element 70. In an embodiment, the wedge-shaped clamp 73 may extend an angle α between approximately 10° and 90° around the periphery of the cutting element 70. In one embodiment, the wedge-shaped clamp extends an angle α of approximately 45° around the periphery of the cutting element. In another embodiment, wedge-shaped clamp 73 may extend an angle α greater than 90°, such as 270°, around the periphery of the cutting element 70. In one embodiment, the cutting element 70 is oriented on the drill bit such that the cutting edge 77 of the thermally stable PCD body 71 engages the formation, such as during a subterranean drilling or mining operation (i.e., the cutting element 70 may be oriented on the drill bit such that the clamp 73 does not engage the formation during a drilling or mining operation). The clamp 73 may be formed by any suitable process, such as extrusion or HPHT sintering. The clamp 73 may be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof. Examples include carbides such as WC, W 2 C, TiC, VC. In an embodiment, the clamp 73 is formed of cemented tungsten carbide. Similarly, the substrate 72 can be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof, such as WC, W 2 C, TiC, VC. In one embodiment, the substrate 722 is formed of cemented tungsten carbide. In an embodiment, the clamp 73 and the substrate 72 are formed from substantially similar materials, although the clamp 73 and the substrate 72 may be formed from dissimilar materials and still fall within the scope and spirit of the present disclosure. In one embodiment, the clamp 73 and the substrate 72 may be formed from cemented tungsten carbide.

After the notch 78 has been formed in the thermally stable PCD body 71, the clamp 73 is seated in the notch 78 with the lip 92 and the flange 82 in an interlocking or lap joint configuration, as illustrated in FIGS. 8 and 9. When the clamp 73 is received in the notch 78 in the thermally stable PCD body 71, a lower surface 94 of the lip 92 rests on the upper surface 84 of the flange 82. Additionally, the step 93 and the end wall segment 88 of the clamp 73 abut the vertical wall segment 83 and the interior wall segment 81 of the notch 78, respectively, as illustrated in FIG. 9. The tapered wall segments 85, 86 of the clamp 73 abut the tapered wall segments 79, 80, respectively, of the notch 78. In another embodiment, the step 93, the end wall segment 88, and the tapered wall segments 85, 86 of the clamp 73 are spaced apart from the vertical wall segment 83, the interior wall segment 81, and the tapered wall segments 79, 80 of the thermally stable PCD body 71, respectively. Moreover, the upper surface 89 of the clamp 73 is substantially coplanar with the working surface 74 of the thermally stable PCD body 71 and the interface surface 90 of the clamp 73 is substantially coplanar with the interface surface 95 of the substrate 72, as shown in FIG. 9.

The thermally stable PCD body 71 and clamp 73 are subsequently positioned on the interface surface 95 of the substrate 72. Together, the thermally stable PCD body 71 and the clamp 73 are substantially coextensive with the interface surface 95 of the substrate 72. Subsequently, the thermally stable PCD body 71, the clamp 73 and the substrate 72 are placed into a press (e.g., a cubic press, a belt press, a toroid press, etc.) and a second HPHT process is then performed to mechanically secure the thermally stable PCD body 71 to the substrate 72 with the clamp 73. In an embodiment, the second HPHT process may be performed at pressures ranging between approximately 5.5 GPa and 7 GPa and temperatures ranging between approximately 1340° C. and 1550° C. In another embodiment, the second HPHT process may be performed at approximately 5 GPa. In one embodiment, the temperature and pressure applied during the HPHT process to bond the clamp 73 to the substrate 72 are substantially similar to the temperature and pressure applied during the HPHT sintering process forming the thermally stable PCD body 71. During the second HPHT process, a metallurgical bond is formed between the clamp 73 and the substrate 72 along the interface surface 90 of the clamp 73. Depending on the conditions of the second HPHT process, a metallurgical bond may also form at the interface between the thermally stable PCD body 71 and the clamp 73. In an embodiment, the carbide clamp 73 becomes ductile during the second HPHT process and a portion of the clamp 73 infiltrates into the interstitial regions between the bonded diamond crystals of the thermally stable PCD body 71, thereby forming the metallurgical bond between the PCD body 71 and the clamp 73. Additionally, in one embodiment, a bond may form between the thermally stable PCD body 71 and the carbide substrate 72 along the respective interface surfaces 75, 95. Accordingly, the metallurgical bond between the clamp 73 and the substrate 72, and the interlocking configuration of the clamp 73 and the notch 78, mechanically secure the thermally stable PCD body 71 to the substrate 72.

In another embodiment illustrated in FIGS. 10-12, a cutting element 130 is formed by mechanically joining a thermally stable PCD body 131 to a substrate 132 with a fastening member 133. As described above, the cutting element 130 is formed by pre-forming the thermally stable PCD body 131 in a first HPHT sintering process and subsequently mechanically joining the thermally stable PCD body 131 to the substrate 132 via the fastening member 133 in a second HPHT sintering process. The thermally stable PCD body 131 includes a working surface 134, an interface surface 135 opposite the working surface 134 and a sidewall 136 extending between the working surface 134 and the interface surface 135. The thermally stable PCD body 131 also includes a cutting edge 137 where the sidewall 136 meets the working surface 134.

In the illustrated embodiment of FIGS. 10-12, an opening 138 having a tapered flange 139 is formed in the thermally stable PCD body 131 to receive the fastening member 133 securing the thermally stable PCD body 131 to the substrate 132. The tapered flange 139 tapers between a thicker portion near the center of the PCD body 131 and a thinner portion proximate the sidewall 136. It will be appreciated that the opening 138 in the PCD body illustrated in FIGS. 10 and 12 is tapered rather than notched as described above with reference to FIGS. 7 and 9. The tapered flange 139 also includes a sloped interface surface 140 (FIG. 12) configured to engage a portion of the fastening member 133, as described below. The opening 138 in the PCD body 131 may be formed by laser cutting, electrical discharge machining (EDM), or any other suitable process known in the art. The opening 138 may also be formed during the first HPHT sintering process.

With continued reference to FIGS. 10-12, the fastening member is a tapered wedge 133 configured to mechanically secure the thermally stable PCD body 131 to the substrate 132. It will be appreciated that the tapered wedge 133 illustrated in FIGS. 10 and 12 includes a sloped interface surface 141 rather than the stepped profile of the clamp 73 described above with reference to FIGS. 7 and 9. The sloped interface surface 141 of the tapered wedge 133 generally matches or is complementary to the shape of the sloped interface surface 140 of the tapered flange 139. The tapered wedge 133 generally complements the opening 138 in the thermally stable PCD body 131 such that the tapered wedge 133 is configured to seat in the opening 138. The tapered flange 139 is configured to underlap a portion of the tapered wedge 133, as illustrated in FIG. 12. Said another way, a portion of the tapered wedge 133 is configured to overlap a portion of the tapered flange 139 in the thermally stable PCD body 131, thereby forming a lap joint securing the thermally stable PCD body 131 to the substrate 132. When the tapered wedge 133 is received in the opening 138 in the PCD body 131, the sloped interface surface 141 of the wedge 133 rests on the sloped interface surface 140 of the tapered flange 139, as illustrated in FIG. 12. The tapered wedge 133 may be formed by any suitable process, such as extrusion, HPHT sintering, laser cutting, or electrical discharge machining (EDM). Additionally, the tapered shape of the wedge 133 may facilitate forming the tapered wedge 133 by grinding.

After the tapered wedge 133 is positioned in the opening 138 in the PCD body 131, the tapered wedge 133 and the PCD body 131 are then stacked on an interface surface 142 of the substrate 132. In one embodiment, the tapered flange 139 does not extend entirely to the sidewall 136 of the PCD body 131 such that an interface surface portion 143 of the tapered wedge 133 which is not tapered rests on the interface surface 142 of the substrate 132. A second HPHT process is subsequently performed to mechanically secure the thermally stable PCD body 131 to the substrate 132 with the tapered wedge 133. The second HPHT process may be performed at pressures ranging between approximately 5.5 GPa and 7 GPa and temperatures ranging between approximately 1340° C. and 1550° C. During the second HPHT process, a metallurgical bond is formed between the tapered wedge 133 and the substrate 132 along the interface surfaces 142, 143 of the substrate 132 and the tapered wedge 133, respectively. Depending on the conditions of the second HPHT process, a metallurgical bond may also form at the interface between the thermally stable PCD body 131 and the tapered wedge 133, and between the thermally stable PCD body 131 and the substrate 132 along the respective interface surfaces 135, 142. Accordingly, the metallurgical bond between the tapered wedge 133 and the substrate 132, and the overlapping configuration of the tapered wedge 133 and the tapered flange 139, mechanically secure the thermally stable PCD body 131 to the substrate 132.

In an embodiment illustrated in FIGS. 13-15, a cutting element 100 is formed by rotatably joining a thermally stable PCD body 101 to a substrate 102 with a fastening member 103. The thermally stable PCD body 101 is configured to rotate (arrow 108) around the longitudinal axis 109 of the cutting element 100 during operation. The thermally stable PCD body 101 includes a working surface 104, an interface surface 105 opposite the working surface 104 and a sidewall 106 extending between the working surface 104 and the interface surface 105. The thermally stable PCD body 101 also includes a cutting edge 107 where the sidewall 106 meets the working surface 104. The cutting edge 107 is the portion of the thermally stable PCD body 101 that engages the formation, such as during a subterranean mining or drilling operation. A thermally stable PCD body 101 rotatably mounted to the substrate 102 presents a rotating cutting edge 107 against the formation, such as during a subterranean mining or drilling operation, which may reduce the wear of the cutting element 100 and thereby prolong the life of the cutting element 100. That is, the cutting edge 107 of the cutting element 100 illustrated in FIGS. 13-15 is configured to rotate (arrow 108) as it contacts the formation, which promotes uniform wear of the cutting edge 107 and tends to prevent excessive wear in a particular localized region of the cutting edge 107.

In an embodiment, the cutting element 100 is formed by pre-forming the thermally stable PCD body 101 in a first HPHT sintering process and subsequently mechanically joining the thermally stable PCD body 101 to the substrate 102 with the fastening member 103 in a second HPHT sintering process. The thermally stable PCD body 101 formed in the first HPHT sintering process may be either non-metal catalyst PCD (such as carbonates, sulfates, hydroxides and iron oxides), binderless PCD, or leached PCD, as described above.

Apertures 110, 111 are subsequently formed in the thermally stable PCD body 101 and the substrate 102, respectively, to receive the fastening member 103 rotatably joining the thermally stable PCD body 101 to the substrate 102. In an embodiment, the aperture in the thermally stable PCD body 101 is comprised of an axial through hole 110 extending along the longitudinal axis 109 of the cutting element 100, and the aperture in the substrate 102 is a generally cylindrical recess 111 concentric with the axial through hole 110. The cylindrical recess 111 in the substrate 102 is comprised of a lower surface 112 and a sidewall 113 extending between the lower surface 112 and the interface surface 114 of the substrate 102.

In an embodiment illustrated in FIGS. 13 and 15, the interface surface 114 of the substrate 102 includes one or more concave recessed portions, such as hemispherical depressions 115. In an embodiment, the hemispherical depressions 115 are disposed in a circular pattern concentric with the cylindrical recess 111. In an embodiment, the interface surface 114 of the substrate 102 may include between approximately four and twenty equidistantly spaced hemispherical depressions 115. In an embodiment, the hemispherical depressions 115 are configured to receive ball bearings 116 on which the thermally stable PCD body 101 is configured to rotate (arrow 108). The hemispherical depressions 115 in the interface surface 114 of the substrate 102 may be formed by machining processes known in the art.

In an embodiment illustrated in FIGS. 13-15, the fastening member is comprised of a pin 103 having a head portion 117 and a relatively smaller shaft portion 118 extending down from the head portion 117. The head portion 117 of the fastening member 103 has opposite top and bottom surfaces 119, 120. The outer diameter of the shaft 118 may be slightly smaller than the diameter of the through hole 110 in the thermally stable PCD body 101 such that the thermally stable PCD body 101 may rotate about the pin 103. In contrast, the outer diameter of the shaft 118 may be substantially equal to the diameter of the cylindrical recess 111 in the substrate 102 to facilitate bonding between the fastening member 103 and the substrate 102. Accordingly, in one embodiment, the diameter of the through hole 110 in the thermally stable PCD body 101 may be slightly larger than the diameter of the cylindrical recess 111 in the substrate 102.

After the apertures 110, 111 have been formed in the thermally stable PCD body 101 and the substrate 102, respectively, and the ball bearings 116 have been inserted into the hemispherical depressions 115, the thermally stable PCD body 101 is positioned on top of the substrate 102 and the apertures 110, 111 are axially aligned. When the thermally stable PCD body 101 is positioned on the substrate 102, the interface surface 105 of the thermally stable PCD body 101 rotatably contacts a portion of the ball bearings 116, as illustrated in FIG. 15. After the thermally stable PCD body 101 has been axially aligned with the substrate 102, the pin 103 may be inserted through the through hole 110 in the thermally stable PCD body 101 and into the cylindrical recess 111 in the substrate 102.

In an embodiment, a small gap may exist between the bottom surface 120 of the head portion 117 of the pin 103 and the working surface 104 of the thermally stable PCD body 101. The gap is configured to permit the thermally stable PCD body 101 to rotate (arrow 108) about the pin 103 during operation. In another embodiment, the bottom surface of the head portion of the fastening member abuts the working surface of the thermally stable PCD body. Similarly, an annular gap may be formed between the pin 103 and the through hole 110 such that the thermally stable PCD body 101 is configured to rotate (arrow 108) about the pin 103 during operation. Additionally, the bottom surface 121 of the shaft 118 of the pin 103 abuts the lower surface 112 of the cylindrical recess 111 in the substrate 102, as shown in FIG. 15. Moreover, the outer surface of the shaft 118 engages the sidewall 113 of the cylindrical recess 111.

Subsequently, the thermally stable PCD body 101, the pin 103, and the substrate 102 are placed into a press (e.g., a cubic press, a belt press, a toroid press, etc.) and a second HPHT process (e.g., pressures ranging between approximately 5.0 GPa and 5.5 GPa, and temperatures ranging between approximately 1300° C. and 1350° C.) is then performed to rotatably join the thermally stable PCD body 101 to the substrate 102 with the pin 103. During the second HPHT process, the pin 103 becomes ductile and a metallurgical bond is formed between the pin 103 and the substrate 102 at the interface between the shaft 118 and the cylindrical recess 111 in the substrate 102. Accordingly, the metallurgical bond formed between the pin 103 and the substrate 102 mechanically secures the thermally stable PCD body 101 to the substrate 102. Moreover, the interface surface 105 of the thermally stable PCD body 101 is slidably engaged with the plurality of bearings 116 recessed in the substrate 102 such that the thermally stable PCD body 101 is rotatably joined to the substrate 102. Accordingly, the PCD body 101 is configured to rotate (arrow 108) about pin 103 during a drilling or mining operation using the cutting element 100. Additionally, insulation in powder or tape form may be provided during the second HPHT process to avoid creating a bond between the pin 103 and the PCD body 101 or between the PCD body 101 and the ball bearings 116, which would tend to resist rotation (arrow 108) of the PCD body 101 relative to the substrate 102. The insulation may comprise any composition which does not react with cobalt under the pressure and temperature conditions of the second HPHT process, such as boron nitride (h-BN) or aluminum oxide (Al₂O₃). The insulation may be removed after the second HPHT process to permit free rotation (arrow 108) of the PCD body 101.

The pin 103 may be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof. Examples include carbides such as WC, W 2 C, TiC, VC. In an embodiment, the pin 103 is formed of cemented tungsten carbide. Similarly, the substrate 102 can be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof, such as WC, W 2 C, TiC, VC. In one embodiment, the substrate 102 is formed of cemented tungsten carbide. In an embodiment, the pin 103 and the substrate 102 are formed from substantially similar materials, although the pin 103 and the substrate 102 may be formed from dissimilar materials and still fall within the scope and spirit of the present disclosure. In one embodiment, the pin 103 and the substrate 102 may be formed from cemented tungsten carbide.

In one embodiment, the cutting element 100 may include a retaining plate 150 disposed between the PCD body 101 and the substrate 102, as illustrated in FIGS. 13-15. The retaining plate 150 is configured to box in the ball bearings 116 (i.e., the retaining plate 150 is configured to prevent the ball bearings 116 from inadvertently dislodging from the depressions 115 in the substrate 102). In the illustrated embodiment, the retaining plate 150 is a circular plate having opposing top and bottom surfaces 151, 152, respectively. The bottom surface 152 of the retaining plate 150 is configured to abut the interface surface 114 of the substrate 102. The retaining plate also includes an axial through hole 153 configured to receive the pin 103 securing the PCD body 101 to the substrate 102. In one embodiment, the diameter of the axial hole 153 is substantially equal to the diameter of the cylindrical recess 111 in the substrate 102. The retaining plate 150 also includes a plurality of radially disposed through holes 154 configured to receive the ball bearings 116. The radially disposed holes 154 are configured to align with the depressions 115 in the substrate 102. As illustrated in FIG. 15, the ball bearings 116 are configured to extend above the top surface 151 of the retaining plate 150 such that the lower surface 105 of the PCD body 101 engages the ball bearings 116. In one embodiment, the retaining plate 150 can be selected from the group including metallic materials, ceramic materials, cermet materials and combinations thereof, such as WC, W 2 C, TiC, VC. In one embodiment, the retaining plate 150 is formed of cemented tungsten carbide, such as 313 grade carbide, 406 grade carbide, 812 grade carbide or any other suitable carbide. In another embodiment, the retaining plate 150 may be formed from the same material as the pin 103, although the retaining plate 150 and the pin 103 may be formed from different materials. The retaining plate 150 may be metallurgically bonded to the substrate 102 during the second HPHT process described above. In one embodiment, the cutting element 100 may be provided without the retaining plate 150.

A method 200 of joining a thermally stable PCD body to a substrate is shown in FIG. 16, according to an embodiment. The method 200 includes forming a thermally stable PCD body 210, which may include forming a non-metal catalyst PCD body 220, forming a binderless PCD body 230 or forming a leached PCD body 240. As discussed above, forming a non-metal catalyst PCD body 220 may include HPHT sintering diamond particles in the presence of a non-metal catalyst, such as carbonate catalyst. Forming a binderless PCD body 230 may include subjecting carbon to an ultra-high HPHT sintering process without a catalyst material, or depositing layers of diamond in a chemical vapor deposition (CVD) process. Forming a leached PCD body 240 may include chemically treating a PCD body following the HPHT sintering process to remove at least a portion of the catalyst material formed in the interstitial spaces or pores between the bonded diamond crystals. In each case, one or more thermally stable PCD bodies may be formed for incorporation into the cutting element (see, e.g., FIGS. 4-12).

The method 200 also includes forming an aperture (such as an axial through hole, a stepped notch or any other suitably shaped opening) in the thermally stable PCD 250, such as by laser cutting or electrical discharge machining (EDM). Forming the aperture in the thermally stable PCD body 250 may include forming a hole 260 or forming a notch 270 in the thermally stable PCD body. In an embodiment, the method 200 may also include forming an aperture in the substrate, such as by milling or machining. The method 200 may also include forming a fastening member, such as a pin or a notched clamp. The fastening member may be formed by any suitable process, such as extrusion or HPHT sintering.

The method 200 also includes inserting the fastening member into the aperture (e.g., an axial through hole or a stepped notch) in the thermally stable PCD body 280. The method 200 also includes bonding the fastening member to a substrate 290, thereby joining the thermally stable PCD body to the substrate. In an embodiment, forming the thermally stable PCD body is performed in a first HPHT sintering process and bonding the fastening element with the substrate is performed in a subsequent second HPHT sintering process. In an embodiment, bonding the fastening element with the substrate 290 includes placing the thermally stable PCD body, the fastening member, and the substrate in a press (e.g., a cubic press, a belt press, a toroid press, etc.) and performing an HPHT process (e.g., pressures ranging between approximately 5.5 GPa and 7 GPa, and temperatures ranging between approximately 1340° C. and 1550° C.).

A method 300 of joining a thermally stable PCD body to a substrate is shown in FIG. 17, according to an embodiment. The method 300 includes obtaining a thermally stable PCD body 310 selected from the group of binderless PCD, non-metal catalyst PCD, and leached PCD. The method 300 may also include forming an aperture in the thermally stable PCD body 320 and forming an aperture in a substrate 330. In an embodiment, forming the aperture in the thermally stable PCD body 320 includes forming an axial through hole, and forming the aperture in the substrate 330 includes forming a cylindrical recess generally concentric with the axial through hole in the thermally stable PCD body. In an embodiment, forming the aperture in the substrate 330 also includes forming a plurality of hemispherical depressions in the interface surface of the substrate.

In an embodiment, the method 300 includes inserting a plurality of ball bearings into the plurality of hemispherical depressions. The method 300 also includes inserting the fastening member into the aperture in the thermally stable PCD body and the aperture in the substrate 340. The method 300 also includes bonding the fastening member to the substrate 350, thereby joining the thermally stable PCD body to the substrate to form the cutting element. In an embodiment, bonding the fastening element with the substrate 350 includes placing the thermally stable PCD body, the fastening member, and the substrate in a press (e.g., a cubic press, a belt press, a toroid press, etc.) and performing an HPHT process (e.g., pressures ranging between approximately 5.5 GPa and 7 GPa, and temperatures ranging between approximately 1340° C. and 1550° C.). In an embodiment, the thermally stable PCD body is rotationally joined to the substrate.

While in one embodiment, the method 200, 300 of joining a thermally stable PCD body to a substrate may include each of the tasks described above and shown in FIGS. 16 and 17, respectively, in other embodiments one or more of the tasks may be absent and/or additional tasks may be performed. Furthermore, in a method of joining a thermally stable PCD body to a substrate according to one embodiment, the tasks may be performed in the order depicted in FIGS. 13 and 14, respectively. However, the present disclosure is not limited thereto and the tasks may be performed in any other suitable sequence. For example, in one embodiment, the task of forming the aperture in the thermally stable PCD body is performed before task of forming the aperture in the substrate, while in another embodiment, the task of forming the aperture in the substrate is performed before the task of forming the aperture in the thermally stable PCD body.

The ultra-hard bodies shown in FIGS. 4-15 are formed as cutting elements for incorporation into a cutting tool. FIG. 18 shows a drill bit 400 incorporating a cutting element 401 including a thermally stable PCD body 402 joined to a substrate 403 by a fastening member 404. The drill bit 400 includes a bit body 405, which may be formed of a matrix material, such as a tungsten carbide powder infiltrated with an alloy binder material, or may be a machined steel body. The bit body 405 includes a threaded connection 406 at one end for coupling the drill bit 400 to a drilling string assembly. An opposite end of the bit body 405 includes a bit face 409 having a cutting element support structure. In an embodiment, the cutting element support structure comprises a plurality of blades 407 extending outward from the bit face 409 and circumferentially disposed around the bit face 409. Each of the blades 407 includes a plurality of cutter pockets 408 to accept and support a cutting element 401 positioned therein. The drill bit 400 may be used for high-temperature rock drilling operations. In other embodiments, other types of drilling or cutting tools may incorporate cutting elements that have a thermally stable PCD body forming at least a portion of the cutting edge of the cutting element, such as, for example, rotary or roller cone drilling bits, percussion or hammer drill bits, or shear cutters.

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this disclosure. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. It is the express intention of the applicant not to invoke 35 U.S.C. 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. Moreover, although the present disclosure has described a fastening member for mechanically joining a thermally stable polycrystalline diamond (PCD) body (such as binderless PCD, non-metal catalyst PCD, and leached PCD) to a substrate, those skilled in the art will appreciate that the present disclosure applies equally to polycrystalline diamond (PCD) bodies and polycrystalline cubic boron nitride (PCBN) bodies. In addition, the thermally stable polycrystalline diamond (PCD) body may be formed with a thermally compatible silicon carbide binder. Additionally, in one embodiment, only a portion of the polycrystalline diamond (PCD) body is thermally stable PCD. For instance, only a portion of the PCD body may be leached and the remainder of the PCD body may be conventional PCD (e.g., the working surface of the PCD body may be leached PCD and the interface surface of the PCD body may be conventional PCD). 

What is claimed is:
 1. A cutting element, comprising: a polycrystalline diamond body having a working surface and an interface surface opposite the working surface; an aperture in the polycrystalline diamond body extending between the working surface and the interface surface; a substrate having an interface surface; a fastening element extending through the aperture in the polycrystalline diamond body; and a metallurgical bond between at least a portion of the fastening element and at least a portion of the substrate at an interface between the fastening element and the substrate.
 2. The cutting element of claim 1, wherein the polycrystalline diamond body is selected from the group of bodies consisting essentially of binderless polycrystalline diamond bodies, non-metal catalyst polycrystalline diamond, leached polycrystalline diamond, carbonate polycrystalline diamond, and polycrystalline cubic boron nitride.
 3. The cutting element of claim 1, wherein at least a portion of the polycrystalline diamond body is selected from the group of bodies consisting essentially of binderless polycrystalline diamond bodies, non-metal catalyst polycrystalline diamond, leached polycrystalline diamond, carbonate polycrystalline diamond, and polycrystalline cubic boron nitride.
 4. The cutting element of claim 1, wherein the fastening member comprises a first carbide material and the substrate comprises a second carbide material, the first carbide material being different than the second carbide material.
 5. The cutting element of claim 1, wherein the fastening member comprises a first carbide material and the substrate comprises a second carbide material, the first carbide material being the same as the second carbide material.
 6. The cutting element of claim 1, wherein the fastening member comprises a cemented tungsten carbide material having a cobalt binder matrix.
 7. The cutting element of claim 1, wherein the metallurgical bond is formed by high pressure high temperature sintering producing a pressure between approximately 5.5 GPa and 7 GPa and a temperature between approximately 1340° C. and 1550° C.
 8. The cutting element of claim 1, further comprising a metallurgical bond between at least a portion of the fastening member and at least a portion of the polycrystalline diamond body.
 9. The cutting element of claim 1, wherein the aperture is a hole extending between the working surface and the interface surface of the polycrystalline diamond body.
 10. The cutting element of claim 9, further comprising a cylindrical recess in the carbide substrate extending down from the interface surface of the substrate, wherein the fastening element is a pin having a head portion and a shaft portion extending from the head portion, the shaft portion extending through the hole and into the cylindrical recess, and the head portion overhanging a portion of the working surface.
 11. The cutting element of claim 1, wherein the aperture is a notch extending along at least a portion of the periphery of the polycrystalline diamond body.
 12. The cutting element of claim 11, wherein the fastening element is a wedge-shaped clamp generally complementary to the notch.
 13. The cutting element of claim 1, further comprising: a plurality of hemispherical depressions in the interface surface of the substrate, wherein the depressions are disposed in a circular pattern; and a plurality of ball bearings housed in the hemispherical depressions, wherein the interface surface of the thermally stable polycrystalline body is slidably engaged with the plurality of ball bearings such that the polycrystalline diamond body is rotatably joined to the substrate.
 14. A drill bit comprising a body having a cutting element as in claim 1 mounted thereon.
 15. A method of joining a thermally stable polycrystalline diamond body to a substrate with a fastening member, the method comprising: obtaining a thermally stable polycrystalline diamond body having an aperture, wherein the thermally stable polycrystalline diamond body is selected from the group of bodies consisting essentially of binderless polycrystalline diamond bodies, non-metal catalyst polycrystalline diamond bodies, leached polycrystalline diamond bodies, carbonate polycrystalline diamond, and polycrystalline cubic boron nitride; obtaining a substrate; inserting the fastening member into the aperture; and high pressure, high temperature sintering the fastening member, the thermally stable polycrystalline diamond body, and the substrate to form a metallurgical bond between the fastening member and the substrate.
 16. The method of claim 15, wherein obtaining the thermally stable polycrystalline diamond body comprises forming the thermally stable polycrystalline diamond body and forming the aperture in the thermally stable polycrystalline diamond body.
 17. The method of claim 16, wherein obtaining the thermally stable polycrystalline diamond body comprises sintering diamond particles and a non-metal catalyst at high temperature and high pressure to form non-metal catalyst polycrystalline diamond.
 18. The method of claim 16, wherein obtaining the thermally stable polycrystalline diamond body comprises subjecting carbon to an ultra-high pressure, high temperature sintering process without a catalyst material, to form binderless polycrystalline diamond.
 19. The method of claim 16, wherein obtaining the thermally stable polycrystalline diamond body comprises: subjecting diamond powder and a catalyst to a high pressure, high temperature sintering process to form a polycrystalline diamond body; and treating a portion of the polycrystalline diamond body to remove a substantial portion of the catalyst material in interstitial regions between the bonded diamond crystals to form leached polycrystalline diamond.
 20. The method of claim 15, wherein high pressure, high temperature sintering the fastening member, the thermally stable polycrystalline diamond body, and the substrate to form a metallurgical bond between the fastening member and the substrate comprises producing a pressure between approximately 5.5 GPa and 7 GPa and a temperature between approximately 1340° C. and 1550° C. 